The original Internet protocol, TCP/IP, was designed on the basis that system users would connect to the network for strictly legitimate purposes; as a consequence, no particular consideration was given to security issues. In recent years, however, the incidence of malicious attacks on the Internet has grown to alarming proportions. Among the various classes of attacks, one could mention denial of service (DoS) attacks, which involve blocking somebody's ability to use a given service on the network, and may take on a variety of forms, and often lead to a complete disruption of service for a targeted victim. Other threats include viruses, worms, system penetration, spoofing, data/network sabotage, data theft, flooding a victim with so much traffic that the victim's server cannot cope, etc.
A computer virus is a program or programming code that replicates itself by being copied or initiating its copying to another program, computer boot sector or document, which replicates across a network in various ways. A virus can be viewed as DoS attacks where the victim is not usually specifically targeted, but simply a host unlucky enough to get the virus. Depending on the particular virus, the denial of service can be hardly noticeable ranging all the way through disastrous. Viruses can be transmitted as attachments to an e-mail note or in a downloaded file, or be present on a diskette or CD. Some viruses wreak their effect as soon as their code is executed; other viruses lie dormant until circumstances cause their code to be executed by the computer. Some viruses are benign or playful in intent and effect and some can be quite harmful, erasing data or causing your hard disk to require reformatting.
A virus that replicates itself by resending itself as an e-mail attachment or as part of a network message is known as a worm. Worms use parts of the operating system that are automatic and usually invisible to the user. It is common for worms to be noticed only when their uncontrolled replication consumes system resources, slowing or halting other tasks. The worms operate by exploiting both known and previously unknown software vulnerabilities in applications and systems software and propagate rapidly across the network. By hijacking trusted applications such as web servers, mail transfer agents and log-in servers, which typically run with many global permission, worms can gain full access to system resources, and cause complete system compromise.
Worms and viruses plague today's data networks and they have been a problem for many years now (Morris worm, Code Red, etc). Unfortunately, these attacks are increasing in frequency, severity, and complexity due to the increasing speed and pervasiveness of broadband connections. These malicious network attacks can particularly harm enterprises and small office/home networks, by denying them the ability to serve their clients, which leads to loss of sales and advertising revenue; the patrons may also seek competing alternatives. It is also known that this type of networks may become exploited and then pose as sources of further malicious activities. It is also known that worms could be much more malicious then have been currently seen. Thus, it is possible to construct hyper-virulent active worms, capable of infecting all vulnerable hosts in approximately 15 minutes to an hour and could cause maximum damage before people could respond. These worms can be built by using optimized scanning routines, hitlist scanning for initial propagation, and permutation scanning for complete, self coordinated coverage.
To protect their network and systems today, enterprises deploy a layered defense model. That includes firewalls, anti-virus systems, access management and intrusion detections systems (IDS), as well as relying on a continuous cycle of patching and reacting to security threats. Defense models have been around for years, and yet to date none have been able to deliver on the final goal of providing full protection against all attacks with little associated cost and annoyance.
Firewalls are vital components in blocking the spreading of malicious activities to and from a given network. The majority of large companies have firewalls in place and security experts still consider they should form the first line of defense in a corporate IT security policy. The currently deployed firewalls can only block a worm if they have the worm specific signature, have the necessary parsing accuracy, or if the worm attempts to use a blocked port or protocol.
Worm signature-based detection systems are based on a network (or per-host), appliance which sits in-line with the network traffic and checks every IP packet against known signatures of worms. Often these solutions also rely on checking traffic flows against bandwidth profiles. Examples of this technology include: Netscreen Intrusion Detection Prevention by Juniper, described at http://www.juniper.net/products/intrusion/, UnityOne by TippingPoint, described at http://www.tippingpoint.com/technology_filters.html and Snort-Inline described at http://sourceforge.net/projects/snort-inline/, to name a few.
Generic in-line Intrusion Prevention Systems (IPS) also rely on signatures and flows measurements to detect and block malicious activities in a network, hence their capabilities are limited in blocking zero-day worms. Moreover, if their detection algorithm is based on statistical observations (e.g. flow's bandwidth, number of active ports per host, etc . . . ) it may take some time before an IPS system can start blocking a worm. Due to this window of time, an enterprise could be held accountable for the spreading of the worm. On the other hand, the proposed invention overcomes the “zero-day” and the “time window” issues by blocking malicious activities with no associated signature at their first attempt.
However, signature and behavior monitoring technologies are not effective the first time a new worm spreads across the Internet, since it is not feasible to setup a policy that recognizes the malicious SW until the attack happens. Signatures and policies can be updated periodically, but only after a worm or other malicious SW has been recognized and studied. Signature monitoring technologies are not effective the first time a new work spreads across the Internet. It is also extremely difficult to distinguish between the identity or behavior of ‘good’ and ‘bad’ code. This results in a large number of ‘false positives’ that limit the purpose of many prevention systems to detecting events rather than protecting against them.
Furthermore, both signature and behavior monitoring techniques allow a time interval between the onset of an attack and its detection, so that by monitoring the behavior of a running application, by the time the destructive behavior is detected, the application is already compromised and the malicious code is already running. This time interval represents a window of vulnerability for a network operating over the attacked access link.
Most importantly, firewalls cannot stop everything; they are configured to allow certain classes or types of data to pass through into the protected network. Every malicious activity that exploits a service allowed through a firewall will successfully spread. As a result, firewalls may no longer be sufficient to protect a corporate network from viruses, system penetration, spoofing, data and network sabotage, and denial of service attacks that exploit vulnerabilities in protocols allowed by a firewall. To address this problem, new techniques are being currently devised.
A DNS (domain name system)-based network security techniques is described by D. White, E. Kranakis, P. C. van Ooschot (School of Computer Science, Carleton University, Ottawa, Ontario, Canada) in the paper entitled “DNS-based Detection of Scanning Worms in an Enterprise Network.”, published in the Proceedings of the 12th Annual Network and Distributed System Security Symposium, San Diego, USA, Feb. 3-4, 2005. The proposal in this paper is based on monitoring the DNS activity before a new connection is established. A scanning worms uses 32 bit random numbers that correspond to an IP address for the infection attempt, so it does not use the DNS protocol for address translation (from the alphanumeric name to a respective IP address).
The Carleton team uses a Packet Processing Engine (PPE), which is constantly observing network traffic, looking for new outbound TCP connections and UDP packets. The captured traffic is passed onto the DNS Correlation Engine (DCE) where it is checked against recently occurred DNS lookups and a whitelist with legitimate applications and services that do not rely on DNS). If a TCP connection is trying to access the Internet without an associated DNS lookup record, the connection is considered anomalous and the system will raise an alarm. The DCE receives DNS lookup information from the local DNS. It also receives allowed embedded numeric IP addresses from the PPE unit, which is parsing HTTP traffic also for this purpose.
However, the work developed by the Carleton team is limited to worm detection, but does not prevent them from spreading. Obviously one successful malicious connection to a host outside a local network could mean that a worm has successfully spread. This means that even if an enterprise network is using this DNS-based detection mechanism to activate some filters to stop a worm from spreading, the enterprise can still be held accountable for the damage caused by the worm during the window of time from detection to reaction. Moreover, the solution presented by the Carleton team requires one or more network appliances that are capable of analyzing in real time, and through deep packet inspection, all traffic leaving the enterprise at every egress point. Each of these traffic analyzers will have to perform line-rate accurate HTML parsing.
In the scope of Self Defending Network, Cisco has proposed a technology called Network Admission Control (NAC) that mitigates the spreading of worms and similar malicious activities within an enterprise network. The idea relies on the enforcement of security policies on any endpoint connecting to a given enterprise network. Cisco NAC grants network access only to compliant and trusted hosts, and restricts the access of noncompliant hosts. The admission decision can be based on several parameters such as the host's anti-virus state and the operating system patch level. If a host is non-compliant, it can be placed in a quarantine zone or be granted minimal access to the network resources.
Cisco's NAC can be considered an indirect worm confinement methodology. In fact, NAC's goal is to ensure that all machines connected to an enterprise network are running updated antivirus software and the latest OS patches. This does not prevent zero-day worms from propagating from the enterprise to the internet. The security provided by NAC is dependent on the enterprise policies and the accuracy of the antivirus software. Moreover, NAC is useless in all those cases where a patch to a specific worm exists but it has yet to be rolled-out due to operational issues.
Alcatel, Inc. also uses an Automated Quarantine Engine (AQE) which is a solution somewhat similar to NAC, but instead of directly verifying the security policy on hosts joining the network, it relies on information collected from intrusion detection and prevention systems and dynamically re-configures the network to contain malicious activities. Upon detection of an attack, the AQE locates the offender and implements a network response. In the case of a virus or worm attack, the AQE will place the infected device into Alcatel quarantine VLAN that is applied to the edge of the network. Using AQE, the infected device will be blacklisted, even if the infected intruder moves to another location.
However, Alcatel's AQE relies completely on third party Intrusion Detection Systems (IDS) in order to block infected hosts. This solution is limited by the IDS system accuracy and by the need for a worm's signature. Moreover, a worm is still able to infect other hosts outside the enterprise network during the window of time between the detection and the quarantining of the infected host. The extent of this time window largely depends on the detection mechanism used by the third party IDS. The proposed solution does not rely on any third party IDS or on any pre-existing signature to confine malicious activities.
In general, all modern technologies involve combinations of the signatures, policies, or training to distinguish between good and bad code, setup is often complex and takes time to roll out across servers. Ongoing tuning and customization is needed to stay current with the latest vulnerabilities and also to reduce the occurrence of ‘false positives’ and ‘false negatives’ identifications of malicious attacks.
The reliability and security of an IP network is essential in a world where computer networks are a key element in intra-entity and inter-entity communications and transactions. Therefore, there is a need to provide a system for confining and detecting malicious activities (e.g. internet worms) in a network that is easy to install and maintain.